The present application finds particular application in controlling screw-type compressors for commercial hybrid vehicles. However, it will be appreciated that the described technique may also find application in other compressor systems, other vehicular systems, or other control systems.
In conventional screw-type compressors, a pair of helical screws or rotors is employed to compress a gas, such as air. Oil-filled screw compressors employ a lubricant that fills the space between the rotors. The lubricant provides a hydraulic seal and transfers mechanical energy between the screws. Air enters at a suction side and moves through the threads as the screws rotate. In this manner, the rotors force the air through the compressor until it exits at the end of the screws.
Trying to drive a liquid-cooled screw compressor under worst case conditions (e.g., less than −5° F., cold startup, no coolant flow into compressor) presents a challenge to the motor controller. Excessive phase and RMS currents can occur, and conventional control strategies are not able to mitigate the over-current conditions or bring the compressor up to working temperature and speed in order to charge the air tanks without blowing fuses, etc.
The present innovation relates to systems and methods that overcome the above-referenced problems and others.